It is often necessary to print large area electrical circuits with conductors having at least one lateral dimension of 1-1000 microns. One process for accomplishing this type of circuit printing is using vacuum deposition. This method, however, is a high-cost operation and is only suitable for batch processing.
Another method of constructing electrical circuits is inkjet printing of patterns using metal nanoparticles to form conductors. This process is discussed in S. Molesa et al.; “High-quality inkjet-printed multilevel interconnects and inductive components on plastic for ultra-low-cost RFID applications.” University of California, Berkeley. Some problems associated with this technique are that it is substrate dependent, it is difficult to achieve lateral dimensions of less than 100 microns, and the particles must be annealed by bulk heating, which can cause substrate deformation. Another problem with inkjet deposition is that it often requires multiple passes to deposit the proper amount of material, which reduces throughput.
Attempts to solve the bulk-heating problem, shown in the following two references, involve using high-powered lasers to anneal nanoparticles. N. R. Bieri et al.; “Microstructuring by printing and laser curing of nanoparticle solutions” Applied Physics Letters, Volume 82, Number 20, May 19, 2003, pages 3529-3531; and J. Chung et al.; “Conductor microstructures by laser curing of printed gold nanoparticle ink” Applied Physics Letters, Volume 84, Number 5, Feb. 2, 2004, pages 801-803. Gold nanoparticles, which are used as an example, have low absorption in the visible spectrum resulting in low heating efficiency. This low heating efficiency is a problem in commercial applications because of low writing speeds.
In the copending U.S. patent application Ser. No. 10/881,301, Yang et al. disclosed a method of forming a pattern of electrical conductors on a substrate by coating metal nanoparticles mixed with a light absorbing dye from a solution on the substrate, and then selectively anneal the metal nanoparticles to conductive material with a laser light.
U.S. Pat. No. 6,770,549 disclosed a method of transferring patterned thin film metal layers from a donor substrate to a receiving substrate by contact adhesion transfer. In this method the pre-patterned metal layers have been formed on the donor substrate by a costly process such as vacuum deposition and sputtering with either a shadow mask or photolithography process.
Laser induced thermal transferring of materials from a donor a donor substrate to a receiving substrate has been disclosed in various prior arts, including U.S. Pat. Nos. 4,948,778; 5,171,650; 5,244,770; 5,256,506; 5,691,098, 5,800,960; 5,981,136; 6,097,416; 6,099,994; 6,190,826; 6,582,877 and 6,866,979, as well as the U.S. Patent Publication No. 2004/0029039, 2004/0028942, and 2003/018638. However, none of them have shown a method or a process that enables the laser induced thermal transferring and annealing of transferred materials at the same time as what is disclosed in the present invention.